This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-078991, filed Mar. 19, 2001; and No. 2001-079458, filed Mar. 19, 2001, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a navigation assisting system, a flight-route calculating method, and a navigation assisting method carried on an airplane which flies as restricted by the ETOPS (Extended Twin Operations).
2. Description of the Related Art
If a twin-engine airplane (airplane equipped with two engines) develops a problem in one of its two engines in flight, it must use the remaining engine to fly to the nearest airport to land. Accordingly, in many cases, twin-engine airplanes are subject to such a restriction that they must fly to be always within 90 minutes of an airport (60 minutes in the USA). This restriction is commonly known to the public as an international rule, based on the international treaty of the ICAO (International Civil Aviation Organization).
On the other hand, ETOPS is provided as a rule for permitting an airplane to prolong its flight time to fly to an airport if the reliability of its engines satisfies certain standards and its operator (e.g., aviation company) satisfies certain safety standards. For example, a state where an arrival time to the nearest airport where take-off and landing are possible is increased to 120 minutes is referred to as xe2x80x9c120-minute ETOPSxe2x80x9d. By adopting this rule, the degree of freedom in the operation of airplanes is enhanced. Moreover, the operators motivation hence the safety of the aircraft can be improved.
Thus, twin-engine airplanes are subject to particular conditions. Because of these conditions, twin-engine airplanes cannot always fly along a direct route from a departure place to a destination. That is, a flight route of a twin-engine airplane is determined so that its arrival time to an airport where it can take off and land, which lies en-route between the point of departure and destination may come within an ETOPS-applied time (that is, 90 minutes, 120 minutes , etc.).
Some of the navigation assisting systems referred to as FMS (Flight Management System) which have been developed recently have a function to automatically calculate a flight route. This function is utilized when a flight plan is prepared before take-off. However, there is no known system that can calculate a flight route taking into account the ETOPS environment.
Furthermore, recent FMSs have a function to warn the pilot if the airplane is about to leave its designated flight-route band when flying. This function is useful when the airplane must deviate from its originally planned flight-path because of bad weather.
This type of existing system, however, does not take into account the ETOPS flight-permitted area. That is, this type of system does not give warning even if the airplane is about to leave the ETOPS flight-permitted area.
Therefore, if the airplane must deviate from its originally-planned flight-path, the pilot must first confirm, by studying a paper map, etc., whether its current flight route satisfies ETOPS environment. It may inflict a heavy burden on the pilot, thus degrade the safety of the flight.
It is an object of the present invention to provide a navigation assisting system and a flight-route calculating method that can calculate a flight route taking into account the ETOPS environment in a flight area.
It is another object of the present invention to provide a navigation assisting system and method which can give a warning, taking into account the ETOPS environment, to mitigate the burden on the pilot, thus contributing to the safety of the flight.
One aspect of the navigation assisting system according to the present invention carried on an airplane includes a storing means for storing a database in which position information of a plurality of airports and information of permission/refusal of take-off/landing of the airplane at the airports correspond to the plurality of airports, respectively, and the regulated time set for the airplane, and an operating means for operating a flight route from which the airplane can fly to an airport where it can take off and land within the regulated time in a flight-permitted area of the airplane.
Such means being thus provided, supposing the airplane to be, for example, a twin-engine one, the operating means calculates such a flight route within the flight-permitted area that satisfies the restriction placed on the airplane that prohibits flying outside an allowed area, to an airport where it can take off and land. Particularly in a case where the regulated time is increased ,using ETOPS, it calculates a flight-permitted area based on the thus increased regulated time.
Thus, a flight route taking ETOPS into account can be calculated by the operating means. This eliminates the need for the pilot to calculate the flight route taking into account the ETOPS conditions. This in turn can mitigate the labor of the pilot and also contribute to safety in operations of the aircraft.
Another aspect of the navigation assisting system according to the present invention carried on an airplane includes a storing means for storing a database in which position information of a plurality of airports and information of permission/refusal of take-off/landing of the airplane at the airports correspond to the plurality of airports, respectively, and the regulated time set for the airplane, and an operating means for specifying as a flight-permitted area of the airplane the inside of a circle having as its radius a distance over which the airplane can arrive within the regulated time also having as its center an airport that the airplane can reach to thereby search the database for the nearest airport where the airplane can take off and land, thus deciding whether the airplane has left the flight-permitted area based on position information of the airplane relative to its flight-permitted area for that nearest airport.
Such means being thus provided, supposing the airplane to be, for example, a twin-engine one, the operating means decides whether the airplane is in a flight-permitted area which satisfies such a restriction that permits flight only in an area from which the airplane can fly to an airport where it can take off and land. If it decides that the airplane has left the flight-permitted area, a message, for example, xe2x80x9cwarningxe2x80x9d is indicated.
Furthermore, even when the airplane remains in the flight-permitted area, if a predetermined point in a traveling direction of the airplane is out of the flight-permitted area, the operating means comes up with a decision that the airplane is in danger of leaving the flight-permitted area. In such a case, a message, for example, xe2x80x9ccautionxe2x80x9d, different from that of the above-mentioned case, is indicated.
In particular, if the regulated time can be prolonged by application of ETOPS, it calculates a flight-permitted area based on this increased regulated time. Moreover, correspondingly, it decides whether the airplane has deviated from the flight-permitted area.
Accordingly, the operating means automatically decides if the airplane has left the ETOPS-flight-permitted area. If it has left it, a message to that effect is given on the display, thus warning the operator. This exempts the operator from the labor of referring to a paper map, thus contributing to safety in operations of the aircraft.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.